Many sealing members such as oil seal, gasket and the like are used to seal refrigerant and freezing machine oil in cooling apparatuses such as refrigerator, freezing machine, air conditioning machine and the like, as well as compressor of air conditioning apparatus and the like. As such sealing member, a sealing member produced by adhering a metal member for a sealing member, which has been applied with an adhesive and baked, and a rubber preformed product using an uncrosslinked rubber composition for forming a sealing member, and forming the rubber preformed product into a rubber formed product is generally known.
As a metal member for the above-mentioned sealing member, a clasp formed from a cold rolled steel plate and the like and applied with a chemical film coating is used, and those treated with a zinc phosphate type film, a zinc calcium phosphate type film, an iron phosphate type film, a manganese phosphate type film and the like are disclosed (patent document 1).
Conventionally, fluorine rubber, nitrile rubber, ethylenepropylene rubber, a mixture of hydrogenated acrylonitrile-butadiene rubber and chlorinated polyethylene and the like have been used as rubber compositions for sealing members. However, there are problems in that rubber formed products using a fluorine rubber show insufficient fluorohydrocarbon resistance, rubber formed products using a nitrile rubber do not show heat resistance under an environment at 150° C., rubber formed products using a mixture of ethylenepropylene rubber or hydrogenated acrylonitrile-butadiene rubber and chlorinated polyethylene are inferior in oil resistance to freezing machine oil such as medicinal oil and the like.
Particularly, since fluorohydrocarbons such as HFC134a(1,1,1,2-tetrafluoroethane; CH2FCF3) and the like, which do not destroy the ozone layer, are used as refrigerants in an air conditioning machine and a freezing machine of vehicles and the like, a rubber formed product used for these sealing members is required to have, in addition to many features of being superior in hardness, elongation, tensile strength, heat resistance and oil resistance, and having small compression permanent strain, fluorohydrocarbon resistance which prevents easy development of crack and blister on contact with fluorohydrocarbon and the like.
In view of such demand, a composition for crosslinked adhesives, which contains a phenolxylylene resin or a phenolbiphenyl resin, a resol type phenol resin and/or a novolac type phenol resin, an uncrosslinked nitrile rubber and chlorinated polyethylene at a particular weight ratio is disclosed as a composition for crosslinked adhesives in consideration of fluorohydrocarbon resistance (patent document 2).
In recent years, however, to save the space of vehicle-mounted parts, an operating temperature of an air conditioning machine for vehicles has increased, and a sealing member such as oil seal, gasket and the like, which is used for a compressor and the like in an air conditioning machine of vehicles, is requested to have heat resistance of a level higher than that of conventional ones. Conventional sealing members have insufficient fluorohydrocarbon resistance when used at a high temperature.